Method for determination of optimal spin axis for a log for peeling in a veneer lathe

ABSTRACT

The invention relates to a method for centering a log for veneer peeling in a lathe. In the method the log is first centered in the centering arrangement of the lathe equipment using centering alignment data based on the contour of the log. On the basis of the thus determined centering data, a computer simulation of peeling is carried out and the results thereof are displayed. The operator performs an alternative centering based on visual evaluation of the log end and, using this centering data, another computer simulation of log peeling is carried out. The peeling outcomes are displayed as an image. The peeling outcomes of all simulations are compared with each other and the centering of actual peeling operation is performed using the centering data giving the optimum yield of peeling.

The invention relates to a visual control method for centering a log in a charging apparatus. i.e. to find a spin axis for the log resulting to an optimal peeling result in the subsequent veneer lathe.

Veneer lathe equipment is still known and widely used in the art where the centering of the log take place under visual inspection of the log end shape, and the log is clamped to the lathe chucks in accordance with the centering result.

To aid the visual centering operation, it is known in the art to project onto the log ends suitable alignment patterns that may comprise, e.g., concentric rings of different diameters. The center of the pattern is the intended spinning center point. Assisted by the projected pattern, the operating personnel of the lathe equipment perform log centering based on long-term experience, where the peeling yield is significantly dependent on the competence of the lathe operator. The peeling results of this arrangement have noted to correlate generally well with results obtained from logs peeled according to centering parameters computed from data received from apparatuses scanning the log contour.

The object of the present invention is to provide a facility for the operator to control the computational log centering procedure, and to give a wider selection of criteria for the determination of log centering parameters. The implementation of the centering method according to invention comprises the steps of first determining the log contour (along the periphery and length of the log), as digital values, and, based on these digital values, computationally determining a spinning axis for the log, performing a computer simulation of veneer peeling based on the detected contour of the log and the determined spinning axis, and displaying the peeling outcome of the simulation as an image. According to the characterizing features of the invention, at least one end surface of the log is displayed as an image, at least one spinning axis is selected for the log by visually evaluating at least the displayed one log end image, a computer simulation peeling is performed based on the digital values of the detected contour of the log and each one of the evaluated spinning axes, the peeling outcome of each peeling simulation is displayed as an image, the peeling outcomes resulting from the use of the computed spin axis and resulting from the use of each visually determined spinning axes are compared with each other, and the spinning axis values for the actual peeling operation are selected from the group: computed spinning axis, each one of the visually evaluated spinning axis.

In the implementation of the invention, the contour of a log to be peeled is determined using a variety of conventional and purposeful equipment capable of digitizing the shape of the log along its periphery and length, whereupon the thus obtained information can be processed computationally.

The contour of a log can be determined along its periphery using conventional devices such as one or more proximity sensors longitudinally displaced at a distance from each other along the length of the log and capable of measuring the distance between the log surface and the sensor. During measurement, the log is rotated about an axis, whereby the entire peripheral shape of the log can be determined. Equipment providing equivalent functions may alternatively be based on sensors recording the log dimensions by optical means. A measurement sensor may also be adapted movable in the longitudinal direction of a log's axis over the entire length of the log. Furthermore, x-ray equipment capable of imaging through the log, are advantageous by virtue of providing additional information from the internal structure of the log. The structural information complements the computation of the numerically controlled peeling thus aiding the determination of optimal peeling parameters.

Useful log shape information may also be obtained by imaging the log ends or at least one of them using digital imaging equipment.

Now operating in accordance with the invention, the practical knowledge of the operator performing the evaluation of the log spinning axis for peeling can be combined by computational means with information gathered from the log contour in order to obtain an optimal spinning axis.

In the method, computer simulated peelings are performed using the log centering parameters received by computational means on the one hand and by the visual evaluation performed by the operator on the other hand, and the peeling outcome of the simulated peelings are displayed as images permitting the operator to select on the displayed virtual peeling results the optimal centering parameters for the lathe, and the selected centering parameters are set for the actual peeling operation.

In a practical implementation of the invention it is also possible that the operator during the centering operation enters data required by the computational centering program, such as information on the minimum radius of the peelable layer for surface quality veneer in the log.

In the following, the invention is elucidated with the help of diagrams displayed to the lathe operator, wherein

FIG. 1 shows the end shape images of a log; and

FIG. 2 shows the peeling outcome of a computer simulation of veneer peeling based on a set of centering parameters.

Referring to FIG. 1, therein the left-side diagram displays the left end of a log while the right-side diagram shows the right end of the log (in regard to the advancing direction of the peeling operation). In the displayed image, the end image denotes the periphery 4 of the log on said end, as well as the first/semi-quality border of the wood on the same log end. Additionally, in the diagram is displayed a ring pattern 5 aiding the centering procedure by way of allowing the lathe operator to displace the log end image relative to the ring pattern in order to determine the optimal turning center point on the basis of his visual evaluation and practical experience.

After the optimal turning center point has been computationally determined based on the scanned contour information of the log, the outcome of the computer simulated peeling is displayed to the operator in the form shown in FIG. 2. In parallel therewith is shown on another display the respective peeling outcome of a computer simulated peeling that is run using the centering parameters based on the operator's visual evaluation of the log, whereupon the operator can perform a comparison between the displayed peeling outcome of the simulated peelings to decide which one of the centering alternatives gives a better peeling yield and, subsequently, enter the centering parameters of the higher yield to be set for the actual peeling operation. Furthermore, the operator has the option to perform a plurality of visual centering operations and to run the respective peeling simulations in order to get plural peeling results for the log to be peeled thus possibly finding a yet higher peeling yield. 

1. A method for centering a log for peeling in a lathe, in which method the log contour is scanned as digital values and, based on the thus determined digital values, computations are performed to determine a digitized optimal spinning axis for the log, a computer simulated peeling is carried out based on the detected contour of the log and the computationally determined parameters of the spinning axis, and finally the outcome of the simulated peeling is displayed as an image, characterized in that, further at least one end surface of the log is displayed as an image, digitized values for at least one further spinning axis are determined for the log by visually evaluating said displayed at least one log end, a computer simulated peeling is performed based on each one of the visually evaluated log spinning axes and the detected contour of the log, the respective peeling outcome is displayed as an image, and the spinning axis parameters for the actual veneer peeling are selected from the group: computationally determined, each one of the visually determined.
 2. The method of claim 1, characterized in that the contour of the log is determined with the help of one or plural machine-vision or proximity sensor devices adapted along the length of the log.
 3. The method of claim 1, characterized in that the shape of the at least one log end is determined with the help of machine-vision equipment.
 4. The method of claim 1, characterized in that the contour of the log is determined with the help of x-ray imaging equipment.
 5. The method of claim 1, characterized in that the results of the simulated peeling operation are complemented With information on the quality parameters of the peeled sheets resulting from the peeling of the log. 